As always, lots of sensible and constructive comments re what I've done to the crank and cases. As mentioned previously, I knew I wouldn't wreck the crank case by boring the bush myself, the worst case scenario would have been another bush and get it done by an engineering company. I have a toolmaking back ground, and everything I've done was considered carefully beforehand.
The reason I very lightly skimmed the shim location area was because the new shims sat on a ridge which locked the crankshaft when, after taking precise measurements I knew that should not be the case. once the ridge had been removed, using the same size shim, the crankshaft ran smoothly. I was aware of the importance of leaving the radius intact.
Regarding the guide I made, fortunately the reamer has an accurately ground long shaft, so the brass bush was machined to fit very snugly into the drive side bearing outer, with the reamer guide hole being accurately bored to size, thus ensuring concentricity between the two locating areas. I did, however allow a couple of thou clearance so that the shank of the reamer would allow me to turn it without the risk of it seizing up in the bush. The bush was made from brass cos that's what I had in stock, in my view, perfectly acceptable as it's just a guide for one off use -nothing is going to "run" in it, so no need for phos. bronze. Just my opinion. If the shank of the reamer had been beaten up through use, I wouldn't have considered doing it, but as it was brand new and unused, everything was on my side. Also, as prev. mentioned, the assembly appears to be fine but I'll only know if it is when I start using the bike. All in all, I'm reasonably content as to the soundness of the work, but if I've buggered it up, it's my own fault.